Method and apparatus for rapid group synchronization

ABSTRACT

A first device of a network may decide to transmit a flood of packets that is longer in duration than the maximum amount of time that the first device can continuously transmit. The first device may coordinate with one or more second devices of the network such that each of the one or more second devices transmits a respective second portion of the flood of packets following transmission of a first portion of the flood of packets by the first network device. The packets may advertise a pending network event that is to occur at a time indicated by the contents of the packets. The first device may select the one or more second devices from a plurality of devices based on a location of the one or more second devices and/or how many third devices are in the network.

CLAIM OF PRIORITY

This patent application is a continuation of U.S. application Ser. No.15/679,798, filed on Aug. 17, 2017, which is a continuation of U.S.application Ser. No. 15/399,251, filed on Jan. 5, 2017, which is acontinuation of U.S. application Ser. No. 15/157,445, filed on May 18,2016, which is a continuation of U.S. application Ser. No. 15/012,888,filed on Feb. 2, 2016, which is a continuation of U.S. application Ser.No. 14/886,151, filed on Oct. 19, 2015, which is a continuation of U.S.application Ser. No. 14/324,411, filed on Jul. 7, 2014 (now U.S. Pat.No. 9,166,894), which is a continuation of U.S. application Ser. No.13/408,457, filed on Feb. 29, 2012 (now U.S. Pat. No. 8,774,096), whichmakes reference to, claims priority to and claims benefit from U.S.Provisional Patent Application Ser. No. 61/464,376 entitled “AdvancedCommunication System for Wide-area Low Power Wireless Applications andActive RFID” and, filed on Mar. 2, 2011.

Each of above-referenced documents is hereby incorporated herein byreference in its entirety.

Incorporation by Reference

This patent application also makes reference to:

-   U.S. Provisional Patent Application Ser. No. 61/464,376 titled    “Advanced Communication System for Wide-Area Low Power Wireless    Applications and Active RFID” and, filed on Mar. 2, 2011, now    expired;-   U.S. Provisional Patent Application Ser. No. 61/572,390 titled    “System for Adding Dash7-Based Applications Capability to a    Smartphone” and, filed on Jul. 15, 2011, now expired;-   U.S. Pat. No. 8,976,691 titled “Method and Apparatus for Adaptive    Searching of Distributed Datasets” and, filed on Oct. 6, 2011;-   U.S. Pat. No. 9,042,353 titled “Method and Apparatus for Low-Power,    Long-Range Networking” and, filed on Oct. 6, 2011;-   U.S. Pat. No. 8,718,551 titled “Method and Apparatus for a    Multi-band, Multi-mode Smartcard” and, filed on Oct. 11, 2011;-   U.S. patent application Ser. No. 13/270,959 titled “Method and    Apparatus for an Integrated Antenna” and, filed on Oct. 11, 2011;-   U.S. patent application Ser. No. 13/289,054 titled “Method and    Apparatus for Electronic Payment” and, filed on Nov. 4, 2011;-   U.S. patent application Ser. No. 13/289,050 titled “Method And    Apparatus For Tire Pressure Monitoring”, filed on Nov. 4, 2011;-   U.S. Pat. No. 8,622,312 titled “Method and Apparatus for Interfacing    with a Smartcard” and, filed on Nov. 16, 2011;-   U.S. Pat. No. 9,104,548 titled “Method and Apparatus for Memory    Management” and, filed on Jan. 20, 2012;-   U.S. patent application Ser. No. 13/354,615 titled “Method and    Apparatus for Discovering, People, Products, and/or Services via a    Localized Wireless Network” and, filed on Jan. 20, 2012;-   U.S. Pat. No. 8,909,865 titled “Method and apparatus for Plug and    Play, Networkable ISO 18000-7 Connectivity” and, filed on Feb. 15,    2012;-   United States Patent Publication No. 2012/0209716 titled “Method and    Apparatus for Serving Advertisements in a Low-Power Wireless    Network” and, filed on Feb. 15, 2012;-   U.S. patent application Ser. No. 13/408,440 titled “Method and    Apparatus for Forward Error Correction (FEC) in a    Resource-Constrained Network” and, filed on Feb. 29, 2012, now    abandoned;-   U.S. Pat. No. 8,867,370 titled “Method and Apparatus for Adaptive    Traffic Management in a Resource-Constrained Network” and, filed on    Feb. 29, 2012;-   U.S. Pat. No. 9,191,340 titled “Method and Apparatus for Dynamic    Media Access Control in a Multiple Access System” and, filed on Feb.    29, 2012;-   United States Patent Publication No. 2012/0226822 titled “Method and    Apparatus for Addressing in a Resource-Constrained Network” and,    filed on Feb. 29, 2012;-   U.S. Pat. No. 8,885,586 titled “Method and Apparatus for Query-Based    Congestion Control” and, filed on Feb. 29, 2012; and-   U.S. Pat. No. 9,154,392 titled “Method and Apparatus for Power    Autoscaling in a Resource-Constrained Network” and, filed on Feb.    29, 2012.

Each of the above-referenced applications is hereby incorporated hereinby reference in its entirety.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to networking. Morespecifically, certain embodiments of the invention relate to a methodand apparatus for rapid group synchronization.

BACKGROUND OF THE INVENTION

Existing methods and systems for synchronizing wireless devices are timeand power intensive. Further limitations and disadvantages ofconventional and traditional approaches will become apparent to one ofskill in the art, through comparison of such systems with some aspectsof the present invention as set forth in the remainder of the presentapplication with reference to the drawings.

BRIEF SUMMARY OF THE INVENTION

A system and/or method is provided for rapid group synchronization,substantially as illustrated by and/or described in connection with atleast one of the figures, as set forth more completely in the claims.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an exemplary wireless communication network in whichnetwork communications may be scheduled as needed and/or on-demand.

FIG. 2 depicts exemplary communication devices which may support rapidgroup synchronization.

FIG. 3A illustrates an exemplary physical layer PDU utilized forsynchronizing network devices and scheduling network events.

FIG. 3B illustrates an exemplary physical layer PDU utilized for datacommunication.

FIG. 4A is a diagram illustrating scheduling of a network communicationvia communications from a single requesting device.

FIG. 4B is a diagram illustrating scheduling of a network communicationvia communications from a single requesting device.

FIG. 5 is a flowchart illustrating exemplary steps for event schedulingin a network comprising a plurality of resource-constrained devices.

DETAILED DESCRIPTION OF THE INVENTION

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (“code”) which may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As utilizedherein, “and/or” means any one or more of the items in the list joinedby “and/or”. As an example, “x and/or y” means any element of thethree-element set {(x), (y), (x, y)}. As another example, “x, y, and/orz” means any element of the seven-element set {(x), (y), (z), (x, y),(x, z), (y, z), (x, y, z)}. As utilized herein, the terms “block” and“module” refer to functions than can be implemented in hardware,software, firmware, or any combination of one or more thereof. Asutilized herein, the term “exemplary” means serving as a non-limitingexample, instance, or illustration. As utilized herein, the terms“e.g.,” and “for example” introduce a list of one or more non-limitingexamples, instances, or illustrations.

FIG. 1 depicts an exemplary wireless communication network in whichnetwork communications may be scheduled as needed and/or on-demand.Referring to FIG. 1, the network comprises base stations/sub-controllers102 ₁ and 102 ₂, and endpoints 104 ₁-104 ₁₆.

Each of the devices 102 ₁ and 102 ₂ may be, for example, a base stationor a network sub-controller and may comprise circuitry for communicatingwirelessly, and managing overall synchronization and access to thewireless network within the cell 108. The devices 102 ₁ and 102 ₂ maytransmit and receive wireless signals in accordance with any one or moreprotocols. Such protocols may include, for example, protocols defined inthe ISO 18000-7 standard, and/or protocols described in theabove-incorporated U.S. Provisional Patent Application No. 61/464,376filed on Mar. 2, 2011. An exemplary device 102 is described below withrespect to FIG. 2.

Each of the endpoints 104 ₁-104 ₁₅ may comprise circuitry forcommunicating wirelessly. Each of the devices 102 ₁ and 102 ₂ maycommunicate with in-range endpoints in accordance with any one or moreprotocols. Such protocols may include, for example, protocols defined inthe ISO 18000-7 standard, and/or protocols described in theabove-incorporated U.S. Provisional Patent Application No. 61/464,376filed on Mar. 2, 2011. An exemplary endpoint 104 is described below withrespect to FIG. 2.

In operation, the devices 102 ₁ and 102 ₂ may send two types of protocoldata units (PDUs) to the devices 104 ₁-104 ₁₅. A first type of PDU(referred to herein as a “background frame”) may be utilized forscheduling the occurrence of events in the network, (e.g., withreference to the common network time and/or common time base), and/orfor other network communications. A second type of PDU (referred toherein as a “foreground frame”) may be utilized for data exchangesand/or other network communications.

The devices 102 ₁ and 102 ₂ may comprise clocks which may be utilizedfor scheduling communications and/or other events in the network.Generally speaking, transmissions in the network may be coordinatedutilizing collision detection and/or collision avoidance, rather than a“fully-managed” or “time-slotted” scheme. As a result, at any giventime, one or more of the devices 104 ₁-104 ₁₅ may be transmitting on themedium, one or more of the devices 104 ₁-104 ₁₅ may be listening on themedium, and one or more of the devices 104 ₁-104 ₁₅ may be in alow-power or powered-down state. Consequently, reliably synchronizingall of the devices 104 ₁-104 ₁₅ may require the transmission of multiplebackground frames in succession. That is, the more background framesthat are consecutively sent, the more likely it may be that any or alldevices 104 ₁-104 ₁₅ have successfully received one of the backgroundframes.

Each of the devices 102 ₁ and 102 ₂ may, however, be limited in how manyconsecutive background frames it can send. Accordingly, aspects of theinvention may enable the devices 102 ₁-102 ₂ to coordinate a flood ofbackground frames where a transmission of one or more background packetson a particular channel by device 102 ₁ is followed immediately (or asnearly immediately as may be possible or permitted) by a transmission ofone or more background packets on the same channel by device 102 ₂. Inthis manner, a flood of background packets twice as long as may be sentby device 102 ₁ or 102 ₂ alone may be achieved. For even longer floods,the devices 102 ₁ and 102 ₂ may coordinate with additional devices 102(not shown) and/or the devices 102 ₁ and 102 ₂ may continue to alternatetransmissions back-to-back for as long as may be desired.

FIG. 2 depicts exemplary communication devices which may support rapidgroup synchronization. Shown in FIG. 2 are details of an exemplary firstdevice 102 _(x) (which may generically represent each of the devices 102₁ and 102 ₂), and details of an exemplary second device 104 _(x) (whichgenerically represents each of the devices 104 ₁-104 ₁₅).

The CPU 204 may comprise circuitry operable to control operation of thefirst device 102. The CPU 204 may, for example, execute an operatingsystem and/or other programs such (e.g., programs that enable a userinterface of the device 102). The CPU 204 may generate one or morecontrol signals for controlling the operation of the device 102. The CPU204 may, for example, control a mode of operation of the device 102.

The CPU 214 may comprise circuitry operable to control operation of thesecond device 104. In some instances, the CPU 214 may be substantiallysimilar to the CPU 204. In instances that the device 102 is lessresource-constrained device, such as a base station or networkcontroller, and the device 104 is more resource-constrained device, suchas a battery-powered tag or a smartcard as described inabove-incorporated U.S. patent application having Ser. No. 13/270,802,the CPU 204 may be less-complex (e.g., comprise fewer gates, utilizeless power, utilize less memory, etc.) than the CPU 214. In oneembodiment, for example, the CPU 204 may comprise a RISC or ARMprocessor, and the CPU 214 may comprise a state-machine having arelatively small number of states (e.g., four states).

The radio 207 may comprise a processor 208 and an analog front-end (AFE)209. The processor 208 may comprise circuitry operable to interface withthe AFE 209 to receive and transmit data, and to process received andto-be-transmitted data. For transmission, the processor 208 may beoperable to receive data from the CPU 204 and/or memory 206, encode,packetize, and/or otherwise process the data to prepare it fortransmission in accordance with one or more wireless protocols, andoutput the data to the AFE 209 for transmission. For reception, theprocessor 208 may be operable to receive data via the AFE 209, processthe received data and output received data to the memory 206 and/or theCPU 204. Exemplary protocols which may be supported by the second device104 include the ISO 18000-7 standard, and protocols described in theabove-incorporated U.S. Provisional Patent Application having Ser. No.61/464,376 filed on Mar. 2, 2011.

The radio 217 may comprise a processor 218 and an analog front-end (AFE)219. The baseband processor 218 may comprise circuitry operable tointerface with the AFE 219 to receive and transmit data, and to processreceived and to-be-transmitted data. In some instances, the basebandprocessor 218 may be substantially similar to the baseband processor208. In instances that the device 102 is less-resource-constraineddevice, such as a base station or network controller, and the device 104is a more-resource-constrained device, such as a battery-powered tag,the baseband processor 218 may be less-complex (e.g., comprise fewergates, utilize less power, utilize less memory, etc.) than the basebandprocessor 208. In one embodiment, for example, the baseband processor208 may be operable to implement more complex signal processingalgorithms (e.g., FEC decoding) than the baseband processor 218.

The analog front-end (AFE) 209 may comprise circuitry suitable forprocessing received and/or to-be-transmitted data in the analog domain.For transmission, the AFE 209 may receive digital data from the basebandprocessor 208, process the data to generate corresponding RF signals,and output the RF signals to the antenna 210. For reception, the AFE 209may receive RF signals from the antenna 210, process the RF signals togenerate corresponding digital data, and output the digital data to thebaseband processor 209. In some instances, the AFE 219 may besubstantially similar to the AFE 209. In instances that the device 102is less-resource-constrained device, such as a base station or networkcontroller, and the device 104 is a more-resource-constrained device,such as a battery-powered tag, the AFE 219 may be less-complex (e.g.,comprise fewer gates, utilize less power, utilize less memory, etc.)than the AFE 209. In one embodiment, for example, the AFE 209 maycomprise a more-sensitive receiver, a more powerful transmitter than theAFE 219.

Circuitry of the memory 206 may comprise one or more memory cells andmay be operable to store data to the memory cell(s) and read data fromthe memory cell(s). The one or more memory cell may comprise one or morevolatile memory cells and/or one or more non-volatile memory cells. Thememory 206 may store data arranged, for example, as an indexed shortfile block (ISFB) and/or indexed short file series block (ISFSB) asdescribed in the above-incorporated U.S. Provisional Patent Applicationhaving Ser. No. 61/464,376.

Circuitry of the memory 216 may comprise one or more memory cells andmay be operable to read data from the memory cell(s) and/or store datato the memory cell(s). The memory 216 may store data arranged, forexample, as an indexed short file block (ISFB) and/or indexed short fileseries block (ISFSB) as described in the above-incorporated U.S.Provisional Patent Application having Ser. No. 61/464,376. In someinstances, the memory 216 may be substantially similar to the memory206. In instances that the device 104 is resource-constrained, thememory 216 may be less-complex (e.g., comprise fewer gates, utilize lesspower, etc.) than the memory 206.

Each of the clocks 211 and 221 may be operable to generate one or moreoscillating signals which may be utilized to control synchronouscircuitry of the device 100. Each of the clocks 211 and 221 maycomprise, for example, one or more crystal oscillators, phase-lockedloops, and/or direct digital synthesizers. Each of the clocks 211 and221 may also comprise a “date/time” or “real-time” clock operable tokeep track of time of day, day of week, day of month, month, and/oryear.

The interfaces 212 and 222 may enable configuring and/or programming thedevices 102 and 104, respectively. In an exemplary embodiment, one ormore values of one or more timing parameters may be programmed via theprogramming interfaces 212 and/or 222.

Each of the antennas 210 and 220 may be operable to transmit and receiveelectromagnetic signals in one or more frequency bands. In an embodimentof the invention, the antennas 210 and 220 may be operable to transmitand receive signals in the ISM frequency band centered at 433.92 MHz.

In operation, the device 102 _(x) may decide to (or be instructed to)schedule a network communication (e.g., schedule a search of the devices104 ₁-104 ₁₅) to occur at time T, where T may be referenced to a commontime base (e.g., ticks of a fixed-frequency oscillator) and/or to areal-time clock. For example, the device 102 _(x) may generate abackground frame that instructs destination devices (i.e. devices forwhich the frame is destined) receiving the background frame to beprepared (e.g., have their receivers on and listening to a particularchannel) to receive a search request at time T. From time T−2Δ untiltime T+Δ, where Δ is some positive value, the device 102 _(x) maytransmit the generated background frame one or more times in succession.The amount of time between transmissions of the background frame may beas short as is permissible and/or allowed. If, during the time periodfrom time T−2Δ to time T+Δ, the device 104 _(x) was listening to thechannel(s) on which the background frame was transmitted, then thedevice may have received the background frame, and scheduled itself toturn on the receive portion of its radio 217 at time T−α (where α is theamount of time that it takes the receiver to power-up and stabilize).

If, on the other hand, the device 104 _(x) was not receiving during theperiod from time T−2Δ to time T+Δ, (e.g., because its receiver was offand/or it was busy transmitting), then the clock 221 may have failed toschedule the reception of the request at time T−α. Consequently, thedevice 104 _(x) may miss the search request and the results of searchmay be sub-optimal.

FIG. 3A illustrates an exemplary physical layer PDU utilized forsynchronizing network devices and scheduling network events. Thephysical layer frame comprises a preamble, a sync word, and a payload.The preamble may be utilized for phase and/or frequency locking thereceive circuitry of the device receiving the PDU. The sync word mayidentify whether the PDU contains a background frame or a foregroundframe. In the case of FIG. 3A, the sync word may indicate that the PDUcontains a background frame.

The payload comprises a data link layer (OSI layer 2) PDU; in this case,a background frame. The background frame comprises a subnet field, abackground protocol ID (BPID) field, and a CRC field. The subnet fieldmay be a value utilized for packet filtering. Specifically, deviceswhich have a device subnet specifier that does not match the value inthe subnet field of the frame may ignore/discard the frame. The CRCfield may be utilized for performing error detection and/or correctionon the received PDU.

The payload comprises a background protocol ID (BPID) field and protocoldata. The BPID may indicate which background frame protocol(s) is to beutilized for parsing and/or processing the received frame. In the caseof FIG. 3A, the background protocol is an advertising protocol, and theprotocol data comprises a channel ID field and an event time field. Foreach devices 104 _(x) that received the frame and determined that it wasa valid destination of the frame, the event time field may indicate atime at which the device should prepare to receive a transmission andthe channel ID field may indicate a channel on which the device 104 _(x)should prepare to receive the transmission. The event time field may beformatted as amount of time until the event and/or real-time at whichthe event will occur.

FIG. 3B illustrates an exemplary physical layer PDU utilized for datacommunication. The physical layer frame comprises a preamble, a syncword, and a payload. The payload comprises a data link layer (OSI layer2) PDU, in this case, a foreground frame. The foreground frame comprisesa length field, a header field, a payload, a footer, and a cyclicredundancy check field. The payload may comprise, for example, a networklayer (OSI layer 3) PDU. The headers field may comprise, for example,TxEIRP field, a subnet field, a frame control field, a data link layersecurity (DLLS) code, DLLS initialization data, a dialog identifier, aflags field, a source ID, and a target ID. The frame control fieldcomprises a listen flag, a DLLS flag, an enable addressing flag, a framecontinuity flag, a CRC32 flag, a not mode 2 flag, and a mode 2 frametype flag. The flags field comprises an addressing option flag, avirtual ID flag, a network layer security flag, and application flags.

FIG. 4A is a diagram illustrating scheduling of a network communicationvia communications from a single requesting device. From time instant T2to time instant T5, the device 102 may begin transmitting backgroundframes to schedule a search at time instant T9. The background framesmay arrive at the device 104 from time instant T3 until time instant T7.The device 104, however, may be transmitting from time instant T1 totime instant T4 and may not begin receiving until T6. As a result, thedevice 104 may not successfully receive one of the background packetstransmitted by the device 102 ₁ from time instant T2 to T5.Consequently, the device 104 may not schedule reception of the searchrequest at time instant T9, and may not participate in the search. Hadthe device 1021 transmitted background packets (e.g., until time instantT8) perhaps the device 104 would have successfully received thebackground frame, but the device 1021 may be prevented from transmittinglonger than the duration of T5−T2.

FIG. 4B is a diagram illustrating scheduling of a network communicationvia communications from a single requesting device. From time instant T2to time instant T5, the device 102 may begin transmitting backgroundframes to schedule a search at time instant T10. The background framesmay arrive at the device 104 from time instant T3 until time instant T7.The device 104, however, may be transmitting from time instant T2 totime instant T4 and may not begin receiving until T6. As a result, thedevice 104 may not successfully receive one of the background packetstransmitted by the device 102 ₁ from time instant T2 to T5. In contrastto FIG. 4A, however, at time instant T5 the device 102 ₂ may begintransmitting the background frame, and the transmissions may arrive atdevice 104 between time instants T7 and T9. The device 104 maysuccessfully receive one of the background frames transmitted betweentime instants T5 and T8 and may, consequently, schedule reception of thesearch to be transmitted at time instant T10. Accordingly, at timeinstant T10−Δ, the device 104 may power-up its receiver, and may receivethe search request from time instant T11 to T13.

FIG. 5 is a flowchart illustrating exemplary steps for event schedulingin a network comprising a plurality of resource-constrained devices. Theexemplary steps begin with step 502 in which a base station (e.g.,device 102 ₁) determines to schedule a network transmission. The networktransmission may be, for example, a search request.

In step 504, the base station may determine an amount of time for whichto transmit background frames advertising the scheduled networktransmission. The duration of the flood of background frames may bedetermined based on a variety of factors such as, for example: how manydevices 104 are present in the network, a distance to one or more of thedevices 104, how frequently the devices 104 typically transmit, howfrequently the devices 104 typically perform a channel scan, powerand/or sources available to the base station (e.g., if it is running onbattery power it may want to reduce the length of the flood), and/oramount of time until the scheduled event.

In step 506, the base station may coordinate with sub-controllers (e.g.,device 102 ₂) in the network to transmit the flood of background frames.The sub-stations may enlist other devices to participate in the floodbecause, for example, the flood will be longer than the base station cantransmit (e.g., because of technical and/or regulatory limitations). Thesub-stations may enlist other devices to participate in the floodbecause, for example, the large number of devices 104 in the networkmakes it unlikely that greater than a threshold percentage (which may beconfigurable and/or vary with the circumstances of the scheduledtransmission) of the devices 104 will receive the background frames ifthe duration of the flood is limited to the maximum duration ofcontinuous transmission by the base station. The sub-stations may enlistother devices to participate in the flood because of the distancebetween the base station and one or more devices in the network. Forexample, based on past communications with the sub-controller and/or thedevices 104, the base station may be aware that the sub-controller maybe closer to one or more devices 104 and thus enable more reliablyreaching those one or more devices. In an exemplary embodiment, the basestation may coordinate with the sub-controller(s) via a differentprotocol (wired, wireless, or optical) than the protocol utilized forcommunicating with the devices 104. For example, the base station andsub-controller(s) may have wired connections to a LAN or the Internet.

In step 508, the base station may transmit its portion of the backgroundframes. Devices which perform a channel scan during this time period maysuccessfully receive one or more of the background frames and mayschedule reception of the pending transmission being advertised in thebackground frames. Devices which do not perform a channel scan duringthis time period may not receive one or more of the background framesand, consequently, may not schedule reception of the pendingtransmission being advertised in the background frames.

In step 510, the sub-controllers with which the base station coordinatedin step 506 may, sequentially in turn, transmit its share of thebackground frames. Devices which perform a channel scan during this timeperiod (which may include devices which did not perform a channel scanduring step 508) may successfully receive one or more of the backgroundframes and may schedule reception of the pending transmission beingadvertised in the background frames.

In another embodiment of the invention, the coordinating of thesub-controllers may comprise controlling their transmit strength suchthat their transmissions are non-overlapping. In this manner, all of thesub-controllers could transmit the flood concurrently.

In step 512, the scheduled transmission (e.g., a search request asdescribed in above-incorporated U.S. patent application Ser. No.13/267,640) may take place at the scheduled time. In an exemplaryembodiment, the scheduled transmission may be transmitted only by thebase station. In another exemplary embodiment, the request may betransmitted concurrently by a plurality of sub-controllers each of whichhas had its transmit power and/or transmit channel configured to notoverlap with other ones of the sub-controllers (i.e., so the packetsfrom the various sub-controllers does not collide).

In an exemplary embodiment of the invention, a first device 102 ₁ of anetwork may decide to transmit a flood of packets that is longer induration than the maximum amount of time that the first device cancontinuously transmit. The first device 102 ₁ may coordinate with one ormore second devices 102 ₂-102 _(N) (where N is an integer greaterthan 1) of the network such that each of the one or more second devices102 transmits a respective second portion of the flood of packetsfollowing transmission of a first portion of the flood of packets by thefirst network device 102 ₁. The packets may advertise a pending networkevent that is to occur at a time indicated by the contents of thepackets (e.g., by an event time field). The network event comprises thetransmission of a search request. The packets may contain a channelidentifier field that indicates a channel on which the search requestwill be transmitted. The device 102 ₁ may select the one or more seconddevices 102 ₂-102 _(N) from a plurality of devices based on a locationof the one or more second devices 102 ₂-102 _(N). The device 102 ₁ mayselect the one or more second network devices from a plurality ofdevices based on how many third devices 104 are in the network. Theplurality of second devices 102 ₂-102 _(N) may concurrently transmittheir respective portions of the flood. A transmit power utilized byeach of the one or more second devices for transmitting its respectiveportion of the flood may be controlled to avoid collisions betweenpackets of the flood. Each one of the plurality of second devices 102₂-102 _(N) may transmit its respective portion of the flood on a channelthat is different than a channel utilized by each other one of theplurality of second devices 102 ₂-102 _(N) for transmitting theirrespective portions of the flood. The packets may be background framescomprising a subnet field, a background protocol identifier field, achannel identifier field, and an event time field.

Other embodiments of the invention may provide a non-transitory computerreadable medium and/or storage medium, and/or a non-transitory machinereadable medium and/or storage medium, having stored thereon, a machinecode and/or a computer program having at least one code sectionexecutable by a machine and/or a computer, thereby causing the machineand/or computer to perform the steps as described herein for rapid groupsynchronization

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputing system, or in a distributed fashion where different elementsare spread across several interconnected computing systems. Any kind ofcomputing system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computing system with a program orother code that, when being loaded and executed, controls the computingsystem such that it carries out the methods described herein. Anothertypical implementation may comprise an application specific integratedcircuit or chip.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

What is claimed is:
 1. A method comprising: in a first device of anetwork: deciding to transmit a flood of packets that is longer induration than the maximum amount of time that said first device cancontinuously transmit; coordinating with one or more second devices ofsaid network such that each of said one or more second devices transmitsa respective second portion of said flood of packets followingtransmission of a first portion of said flood of packets by said firstnetwork device.
 2. The method of claim 1, wherein said packets advertisea pending network event that is to occur at a time indicated by thecontents of said packets.
 3. The method of claim 2, wherein said networkevent comprises the transmission of a search request.
 4. The method ofclaim 3, wherein said packets contain a channel identifier field thatindicates a channel on which said search request will be transmitted. 5.The method of claim 1, comprising selecting said one or more seconddevices from a plurality of devices based on a location of said one ormore second devices.
 6. The method of claim 1, comprising selecting saidone or more second network devices from a plurality of devices based onhow many third devices are in said network.
 7. The method of claim 1,wherein: said one or more second devices is a plurality of seconddevices; and said plurality of second devices concurrently transmittheir said respective portions of said flood.
 8. The method of claim 7,wherein a transmit power utilized by each of said one or more seconddevices for transmitting its said respective portion of said flood iscontrolled to avoid collisions between packets of said flood.
 9. Themethod of claim 7, wherein each one of said plurality of second devicestransmits its said respective portion of said flood on a channel that isdifferent than a channel utilized by each other one of said plurality ofsecond devices for transmitting their said respective portions of saidflood.
 10. The method of claim 1, wherein said packets are backgroundframes comprising a subnet field, a background protocol identifierfield, a channel identifier field, and an event time field.
 11. A systemcomprising: a first device of a network, said first device beingoperable to: decide to transmit a flood of packets that is longer induration than the maximum amount of time that said first device cancontinuously transmit; coordinate with one or more second devices ofsaid network such that each of said one or more second devices transmitsa respective second portion of said flood of packets followingtransmission of a first portion of said flood of packets by said firstnetwork device.
 12. The system of claim 11, wherein said packetsadvertise a pending network event that is to occur at a time indicatedby the contents of said packets.
 13. The system of claim 12, whereinsaid network event comprises the transmission of a search request. 14.The system of claim 13, wherein said packets contain a channelidentifier field that indicates a channel on which said search requestwill be transmitted.
 15. The system of claim 11, wherein said firstdevice is operable to select said one or more second devices from aplurality of devices based on a location of said one or more seconddevices.
 16. The system of claim 11, wherein said first network deviceis operable to select said one or more second network devices from aplurality of devices based on how many third devices are in saidnetwork.
 17. The system of claim 11, wherein: said one or more seconddevices is a plurality of second devices; and said plurality of seconddevices concurrently transmit their said respective portions of saidflood.
 18. The system of claim 17, wherein a transmit power utilized byeach of said one or more second devices for transmitting its saidrespective portion of said flood is controlled to avoid collisionsbetween packets of said flood.
 19. The system of claim 17, wherein eachone of said plurality of second devices transmits its said respectiveportion of said flood on a channel that is different than a channelutilized by each other one of said plurality of second devices fortransmitting their said respective portions of said flood.
 20. Thesystem of claim 11, wherein said packets are background framescomprising a subnet field, a background protocol identifier field, achannel identifier field, and an event time field.